The system is complete aside from a few aesthetic and convenience modifications! This thread is fairly long so I'll summarize the key points here.

This is an all electric fly-sparge based two-vessel system utilizing a MLT & kettle. A high wattage 5500w electric element is used as a dual purpose external heater. The first role of the heater is for heating the recirculated mash. The 2nd role is to directly heat sparge water from ground temps to mash out temps.

Key advantages of the system:

Smaller footprint since there's only 2 vessels.
Quick mash stepping.
Energy efficient, since water is heated directly as needed.
Drain is on bottom of vessels. No dead space and easy to clean.

Original Post:

First, I'd like to thank everyone here on hbt. Nearly all of my info has come from you guys and I don't think I would have attempted this build without reading about everyone else's.

My original plan was to go with an all electric HERMS system, which used a RIMS style heating element in a pipe and a plate style counterflow heat exchanger(hex). I decided to try RIMS first, mostly because it's more simple and I wouldn't have to change a lot of tubing around during the brew session. I plan on testing the HERMS config in the future. The benefit of the larger surface area for heating the mash is too appealing to pass up.

I'll be using a BCS-460 controller. It's basically a microcontroller box which is accessed via a web-based interface. The BCS will PID control the heater elements via solid state relays. More info about the controller can be found at embeddedcontrolconcepts.com. The BCS will monitor three temperature probes and control two heater elements (rims & kettle), plus the two pumps.

Here's my plan for the mash, sparge, and cooling setup. As you can see in the diagrams, I do not plan on using an HLT. The 5500w heater will serve as an inline tankless water heater during the fly sparge. The benefits of only having two vessels is very appealing to me. I do have provisions to add a HLT later if it doesn't work out.

Most of the parts are in. Priority #1 is testing the RIMS heater in tankless water heater mode. Because of this, I'm focusing on electrical and control first with the kettles and and sculpture last. The electrical enclosure is nearly complete and I installed a 50 amp GFCI breaker and outlet this morning. I was a little intimidated at first but I was extremely meticulous and everything worked out well.

Here's a pic of the breaker box with the cover off. The 240V 50A GFCI breaker is the big one in the middle right. The 3 wire+ground cable was run down to an external NEMA 14-50R outlet. The 6gauge wire was a pain to work with even though it's stranded.

Here you can see the external outlet and the control box. A NEMA14-50 range cord works great for this application since it's mass produced (cheap) and already has terminal rings attached. I tested the system by controlling the little AC fan sitting on top of the enclosure.

Here's the guts of the enclosure box. It's a fiberglass reinforced plastic enclosure, NEMA 4X (splash proof) rated from McMaster. The main lines from the range cord are 6 gauge going to the large terminal block which is used for the 240V heater elements. The smaller terminal block is for the lower current 120V components (pumps, controller). Once I have the sculpture built I'll run the output lines. I plan on mounting the fan inside the box to cool the SSR heat sinks.

Here's a pic of the RIMS heater parts. The smaller element is a high density 5500w, slightly bent so it won't hit the sides of the 1.5" ID pipe. The bigger element is a 5500w ultra low watt density that I'll use for the kettle.

I plan on assembling the RIMS heater and testing the tankless water heater functionality in the next several days.

I'm curious about the heating capacity of your "tankless" water heater at full volume.

Due to the small-ish surface area of the heating element and short contact time, I can't imagine it will support an 100F differential (ground water: 70F, sparge water: 170F). But, you might be able to achieve that differential if you severely reduce the flow rate through the pipe...

Also, installing a 5,500w element in a RIMS heat exchanger is not normally recommended because of the potential for scorching and excessive caramelization during the mash. Personally, I went with a 1,500w ultra low density element to help me sleep better at night and, potentially, during the mash.

The smaller element is a high density 5500w, slightly bent so it won't hit the sides of the 1.5" ID pipe. The bigger element is a 5500w ultra low watt density that I'll use for the kettle.

I agree Lamarguy and Slimer. A 5500 watt high density element in the RIMS heater tube to heat the Strike and Sparge is not practical. He will never hit Strike and Sparge Temperatures and when he recirculates his mash and with the high density element, he will scortch his mash for sure.

He will definitely need something like a 1500 watt low density element in the RIMS heater and heat his Strike and Sparge via other means.

I have two boxers also. The first one terrorized me until I got her a friend. They really are great dogs.

You guys pretty much nailed my top two concerns. Since there's no reservoir, I will definitely be limiting the flow. I'm a batch sparger, so fly sparging is new territory for me. From what I've read, fly sparging occurs at rates around 1 quart per minute or even slower. So assuming for a 10 gallon batch, 20lbs of grain, and 36qt of sparge water, I would need to heat 36 quarts of water over a 36 minute time span.

I did some calculations to see if it was feasible. My calculations show a 5500w element should heat 36 quarts of water 100F higher in 24 minutes, ideally:

That's assuming 100% efficiency of course. I'm directly injecting heat into the water and the only losses I can foresee is heat loss from the rims piping and through the lines, both of which should be minimal. I don't see any reasons not to expect very high efficiency. Even 80% efficiency would put it at 30 minutes. I may have to sparge slower in the winter, depending on efficiency and ground temps.

I'll try to test it today and prove you guys wrong. All I really need to do is teflon up the piping and run a couple wires and tubing.

I don't think I'll have scorching issues. I intentionally made the pipe the smallest diameter possible to allow the fastest flow over the element. I also have the ability to control the individual PID parameters, so in theory be able to throttle the heater.